THE EFFECT OF MALATHION, AN ORGANOPHOSPHATE, ON THE PLASMA FSH, 17-BETA-ESTRADIOL AND PROGESTERONE CONCENTRATIONS AND ACETYLCHOLINESTERASE ACTIVITY AND CONCEPTION IN DAIRY-CATTLE

The effect of malathion on jugular plasma concentrations of follicle-s timulating hormone (FSH), estradiol (E2), progesterone (P4) and acetyl cholinesterase (AchE) on conception in dairy cattle during a cloproste nol (prostaglandin F2-alpha analogue, PG)-induced estrus was studied. Malathion (1 mg/kg, intraruminally) given at the onset of estrus (48 h after PG) did not alter the plasma FSH or E2 concentrations but signi ficantly (P < 0.05) inhibited plasma P4 concentration. The mean P4 con centration in the malathion-treated group on days 8 and 12 were 0.8 +/ - 0.4 and 1.0 +/- 0.5 ng/ml, as compared to 2.6 +/- 0.0 and 2.4 +/- 0. 3 ng/ml in the control group. There was a nonsignificant (P > 0.05) in hibition of plasma AchE activity in malathion-treated cattle. Concepti on was 16.6% in malathion-treated cows and 50% in controls. Inhibition of progesterone secretion and poor conception occurred after the sing le intraruminal dose of malathion at the onset of estrus.